Rotary rock bit with cone mouth air screen

ABSTRACT

Drill cuttings in the borehole are prevented from entering the area between the bearing pin and the cone cutter of a rotary rock bit by a cone mouth air screen. The cone cutter includes an internal cavity and a cone mouth positioned over the bearing pin. Bearings are located within the internal cavity between the bearing pin and the cone cutter. A passage extends through the bit body and the bearing pin for conducting a gaseous drilling fluid to the internal cavity for cooling the bearings. A screen means is positioned in the cone mouth between the cone cutter and the bearing pin for preventing solids in the borehole from entering the internal cavity and for allowing the circulating gaseous drilling fluid to pass from the internal cavity into the borehole.

United States Patent [191 Dysart [451 Nov. 25, 1975 ROTARY ROCK BIT WITH CONE MOUTH AIR SCREEN [75] Inventor: Theodore Rivers Dysart, Dallas,

Tex.

[73] Assignee: Dresser Industries, Inc., Dallas, Tex.

[22] Filed: Feb. 27, 1975 [21] Appl. No.: 553,763

[52] US. Cl. 175/337; 175/339; 175/372; 308/82 [51] Int. Cl. EZlB 9/10; E21C 13/00; E21B 9/35', F16C 33/78 [58] Field of Search 175/337, 339, 340, 371, 175/372, 227, 228, 229; 308/82 [56] References Cited UNITED STATES PATENTS 3,193,028 7/1965 Radzimovsky 175/372 3,534,823 10/1970 Frederick 175/337 3,680,873 8/1972 Garner 308/8.2 UX 3,713,707 l/l973 Bennett 308/82 Bell 175/228 Jackson 175/228 [57] ABSTRACT Drill cuttings in the borehole are prevented from entering the area between the bearing pin and the cone cutter of a rotary rock bit by a cone mouth air screen. The cone cutter includes an internal cavity and a cone mouth positioned over the bearing pin. Bearings are located within the internal cavity between the bearing pin and the cone cutter. A passage extends through the bit body and the bearing pin for conducting a gaseous drilling fluid to the internal cavity for cooling the bearings. A screen means is positioned in the cone mouth between the cone cutter and the bearing pin for preventing solids in the borehole from entering the internal cavity and for allowing the circulating gaseous drilling fluid to pass from the internal cavity into the borehole.

5 Claims, 3 Drawing Figures U5. Patent Nov. 25, 1975 Z/Z m FIG. 3

FIG. 2

ROTARY ROCK BIT WITI-I CONE MOUTH AIR SCREEN BACKGROUND OF THE INVENTION The present invention relates to the art of earth boring and more particularly to an improved rotary rock bit for use with a drilling system that utilizes a gaseous drilling fluid.

During certain drilling operations such as the drilling of blast holes, air or other gaseous drilling fluids are circulated through the drill string and the drill bit. The drill bit is attached to a hollow drill string and the gaseous drilling fluid is pumped through the drill string into the bit and thereafter through passages in the bit to the bottom of the borehole, thence upward in the annulus between the drill string and the walls of the borehole to the surface. Some of the passages divert part of gaseous drilling fluid to the bearing spaces between the rolling cutter members and their associated shafts to cool these elements and to keep such spaces cleared from foreign matter and abrasive products.

During drilling operations wherein a gaseous fluid is circulated through the bit with some of the circulating fluid being directed through the bit bearings for cooling and flushing of the bearing components, conditions often exist where the air pressure and volume is inadequate for optimum flushing of the bearings. Under these conditions, the cuttings generated by the bit action on bottom cannot be efficiently lifted off the bottom of the borehole and tend to fall back to the bottom until a time when regrinding by the bit reduces the individual particles to a size small enough to be lifted by the low volume of circulating fluid. It can readily be appreciated that a bit working in a deep bed of cuttings with an insufficiency of fluid flushing through the bearings will be subjected to said cuttings filtering into the bearings. In the bearings, the cuttings will be caught up between the rotating bearing members creating an abrasive grinding-millingwearing action which is extremely detrimental to the entire bearing cluster, and is a major factor in reducing bit bearing life.

The present invention provides a cone mouth air screen which will act as a barrier to the pulverized cuttings, keeping these cuttings from entering the bearing area through the cone mouth opening, thus providing a clean dust-free environment for the metal bearing elements and eliminating the abrasive wearing action mentioned above. The screening out of the dust particles will vastly improve the bearing life by preventing abrasive cuttings from entering the bearings and con tributing to wear of the individual bearing components and thereby contributing to the ultimate failure of the full bearing cluster. Abrasive wear is considered a major factor in limiting bearing life in blast hole drilling bit applications and is especially significant in conditions where the air volume is marginal. This latter condition exists when air compressor equipment has been neglected and does not perform up to its rated capacity or as is common with the smaller blast hole drills, the air volume rating of the compressor is marginal to start with.

DESCRIPTION OF PRIOR ART In U.S. Pat. No. 3.125.175 to J. D. Medlock et al, pa-

tented May I7, 1964, and assigned to Hughes Tool Company, a rock bit with a replaceable air course is shown. The rock bit shown in this patent contains means whereby a portion of the gas stream is diverted into the bearing spaces between the rolling cutters and their shafts thereby flushing and cooling the bearing surfaces. Means are provided within the central body of the bit to prevent the introduction of particular matter into the bearings from the gas being circulated through the drill string.

In U.S. Pat. No. 3,534,823 to Charles R. Frederick, patented Oct. 20, 1970, and assigned to J. W. Murphy Industries, Inc., an improved drill bit is shown. The improved drill bit has a gaseous circulation system for the roller cutters to be used in gas drilling so that a portion of the gas which is circulated through the drill is circulated through the roller cutters to cool the cutter bearings.

SUMMARY OF THE INVENTION The present invention provides a cone mouth air screen whichwill act as a barrier to pulverized cuttings in the borehole and prevent the cuttings from entering the bearing area through the cone mouth opening of the cone cutter. The present invention provides a clean dust-free environment for the bearing elements and eliminates abrasive wearing action arising from the entry of solid particles from the borehole into the bearing area. The bit of the present invention includes a bit body having a bearing pin. A cone cutter is mounted on the bearing pin. The cone cutter includes an internal cavity and a cone mouth. Bearing means are located in the bearing area between the cone cutter and the bearing pin for supporting the cone cutter for rotation about the bearing pin. A first passage extends through the bit body to the internal cavity to allow a portion of the circulating fluid to be directed to the bearings. A second passage extends through the bit body to the exterior of the bit to allow a portion of the circulating fluid to be transmitted to the bottom of the bore.

Screen means are positioned in the cone mouth between the cone cutter and the bearing pin to prevent the entry of solids into the internal cavity and at the same time allow the circulating fluid passing through the internal cavity to exit into the borehole. The above and other features and advantages of the present invention will become'apparent from a consideration of the following detailed description of the invention when taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view ofa portion ofa rotary rock bit constructed in accordance with the present invention.

FIG. 2 is an enlarged view of a portion of the bit shown in FIG. 1.

FIG. 3 shows the cone mouth air screen of the bit shown in FIG. 1.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawings and in particular to FIG. 1, a rotary rock bit 10 constructed in accordance with the present invention is illustrated. The bit 10 includes a bearing pin 12 depending from the main body of the bit 10. The body of the bit 10 defines an internal chamber 41 which during drilling is in communication with the interior drilling fluid passage of a rotary drill string (not shown). A gaseous drilling fluid is circulated through the rotary drill string passing into the internal chamber 41 during the drilling operation.

A rotary cone cutter 14 is mounted on the bearing pin 12. The cone cutter 14 includes an internal cavity for receiving the bearing pin 12. Bearing means are provided between the cone cutter 14 and bearing pin 12 within the internal cavity. The opening of the internal cavity at the base of the cone cutter 14 constitutes a cone mouth. The bearing means include a system of roller bearings 20, a system of ball bearings 18, a friction bearing 24 and a thrust button 22. A multiplicity of tungsten carbide inserts 16 are embedded in the outer surface of the cone cutter 14 for disintegrating the formations as the bit is rotated and moved downward.

In order to prolong the life of the bit and to cool the bearings a gaseous drilling fluid is circulated through the internal cavity in the cone cutter 14 between the cutter l4 and the bearing pin 12. Drilling fluid from the rotary drill string (not shown) passes into the internal chamber 41. A pair of passages 26 and 28 conduct the drilling fluid from the internal chamber 41 to a bore 30 extending through the bearing pin 12. The drilling fluid passes through the bore 30 and an auxiliary passage 32 into the internal cavity in the cone cutter 14 to cool the bearings. The ball loading bore 30 is filled with a plug 34 to retain the individual ball bearings in the ball bear ing system 18. The plug 34 does not entirely fill the bore 30 and allows free fluid passage. The plug 36 is welded in position in the bore 30 by the weld 36. The gaseous drilling fluid exits through the cone mouth into the borehole and travels upward in the annulus between the wall of the borehole and the rotary drill string. Drilling fluid is also directed through a passage 42 from the internal chamber 41 directly into the borehole to remove the drill cuttings from the borehole. The passage 42 directs the circulating drilling fluid proximate the cone cutter 14.

Conditions at times exist where the pressure and volume of the circulating drilling fluid is inadequate for optimum flushing of the bearings. Under these conditions, the cuttings generated by the action of the bit on the bottom of the bore-hole cannot be efficiently lifted off the bottom and they tend to fall back to the bottom until a time when regrinding by the bit reduces the individual particles to a size small enough to be lifted by the low volume of circulating fluid. lt can readily be appre- I ciated that a bit working in a deep bed of cuttings with an insufficiency of fluid flushing through the bearings will be subjected to said cuttings filtering into the bearings. In the bearings, the cuttings will be caught up between the rotating bearing memberscreating an abrasive grinding-milling-wearing action which is extremely detrimental to the entire bearing cluster. Abrasive wear is considered a major factor in limiting bearing life in blast hole drilling bit applications and is especially significant in conditions where the fluid volume is marginal. This latter condition exists when air compressor equipment has been neglected and does not perform up to its rated capacity or as is common with the smaller blast hole drills, the fluid volume rating of the compres sor is marginal to start with.

A cone mouth air screen 40 is provided in the cone mouth of the cone cutter 14. This cone mouth air screen is intended to cover the entire cone mouth area and is of a mesh size such that it will screen out even the smallest particle sizes. For this purpose, a metallic fibermetal screening material is used for the cone mouth air screen 40. This material lends itself well to this application since it has very low density (high porosity) characteristics while retaining good strength properties. The screen material is selected so that its porous area is such that it will allow passage of all the air needed to cool and clean the bearings with a minimum of back pressure, but still fit satisfactorily into the minimal available space at the constricted cone mouth of a typical cone arm sub-assemblyfor a three cutter blast hole bit.

The cone mouth air screen 40 is fitted on the bearing pin 12 in the area of the cone mouth. This same area is. that area which is utilized on prior art sealed bearing bits for the cone mouth seal recess. The cone mouth air screen 40 may be likened to a cone mouth seal except that the screen 40 .will allow the clean fluid in the internal cavity of the cone cutter 14 to escape by offering minimal resistance to fluid flow in one direction while preventing the solid materials in the borehole from entering the internal cavityand by offering maximum resistance to solid materials in the borehole.

Referring now to FIG. 2 an enlarged view ofa portion of the cone mouth area of the bit 10 is shown. The cone mouth air screen 40 is positioned between the cone cutter l4 and the bearing pin 12. The cone mouth air screen 40 is held in place by a rubber ring 38 extending from the air screen 40 that fits around the bearing pin l2.The screen 40 can be locked in place by gluing the rubber portion or simply by sizing the screen such that.

it has some interference with the journal boss over which it fits. In prior art blast hole bits, the cone mouth clearance has traditionally been left fairly generous, or

(if this backface clearance is designed on the tight side), partially open vent slots of varying configurationshave been provided in order to insure minimum restrictions to air flow through the bearings. The cone mouthair screen 40 is the first known attempt to screen out the dust particles at the exit end of the fluid flow passage through the bearing area. The air pressure (and flow) is therefore from the inside toward the outside of the screen and dust particles will be prevented from collecting on the screen by the positive air pressure inside the bearing area.

Referring now to FIG. 3 the cone mouth air screen 40 is shown individually. The cone mouth air screen 40 is intended to cover the entire cone mouth area and should be of a mesh such that it will screen out even the smallest particle sizes. For this purpose, metallic fibermetal screeningmaterials lend themselves well since they have very low density (high porosity) characterisment of the invention is a fiber metal of low to mediums density (less than 40% density by volume) made asa multi-filament of relatively fine (less than 0.001 inch) filament diameter. The preferred filament material is a stainless steel. Other materials such as fiberglass, po-

rous plastic foam, brass or bronze micro beads, etc.. i may also be used for screen 40 and will perform essen tially the same task as the fiber metal. Also, material densities above 4071 by volume may be used if a large exit area is designed into the bit. but at no time is a density of more than by volume acceptable forthis type of screening application. The preferred filament material is stainless steel, but other steels, copper or other metallics, plastic. etc. may be utilized satisfactorily. While filament diameters of 0.001 inch or less are preferred, it is to be understood that other filament sizes may be used including filaments of up to 0.010 inchdiameter.

The structural details of an earth boring bit constructed in accordance with the present invention having been described,the operation of the bit will now be considered with reference to FIGS. 1., 2 and 3. The

present invention provides a cone mouth air screen 40 which will act as a barrier toxthe pulverized cuttings, keeping these cuttings from entering .the bearing area through the cone mouth opening, thus providing a clean dust free environment for the metal bearing elements and eliminating the abrasive wearing action of cuttings in the bearing area. The screening out of the dust particles will vastly improve the bearing life by preventing abrasive cuttings from entering the bearings and contributing to wear of the individual bearing components and thereby contributing to the ultimate failure of the full bearing cluster.

The bit 10 is connected as the lowest member of the rotary drill string. A gaseous drilling fluid is circulated through the drill string to the internal chamber 41 in the bit 10. A portion of the gaseous drilling fluid passes from internal chamber 41 through passage 26, passage 28 and bores 30 and 32. This portion of the gaseous drilling fluid is directed into the internal cavity in the cone cutter 14 to cool the bearings and flush any foreign materials from the bearing area. The cone mouth air screen 40 allows the gaseous drilling fluid to exit into the borehole and serves to prevent drill cuttings from building up on the outside of the air screen 40. The rubber ring 38 locks the air screen in place on the bearing pin 12. The screening out of drill cuttings from the bearing area vastly improves bearing life by preventing abrasive cuttings from entering the bearing area and contributing to wear of the individual bearing components and thereby contributing to the ultimate failure of the full bearing cluster. Abrasive wear is. considered a major factor in limiting bearing life in blast hole drilling bit applications and is especially significant in conditions where the gaseous drilling fluid volume is marginal. Such conditions often exist when air compressor equipment has been neglected and is not performing up to its rated capacity or as is common with the smaller blast hole drills, the fluid volume rating ,of the compressor is marginal to start with.

The embodiments of an invention in which an exclusive property or privilege is claimed are defined as follows:

l. A drill bit for connection with a drill string that includes a drilling fluid passage, comprising:

a body; a bearing shaft supported from said body; a roller cutter adapted to be rotatably mounted on said bearing shaft; bearing means supporting said cutter on said bearing shaft; a passage within said body adapted to be in communication with the drilling fluid passage in said drill string when said drill bit is connected to the drill string; a passage in said bearing shaft communicating between said passage within said body and said bearing means; and

' a 'leg depending from said head;

said leg terminating in a bearing'shaft;

a roller cutter adapted to be mounted on said bearing shaft;

bearing means supporting said roller cutter for rotation about said'bearin'g shaft;

a first passage through said leg and said bearing shaft,

communicating from said internal chamber to a position between said shaft and said cutter;

a second passage extending through said bit communicating from said internal chamber to the exterior of said bit, whereby a first portion of the fluid being circulated through said internal chamber is circulated through said first passage, between said shaft and said cutter to cool said bearing means and a second portion of the fluid being circulated through said internal chamber is circulated through said second passage proximate said roller cutter; and

screen means positioned between said cutter and said shaft for preventing entry of solids to said bearing means and allowing said first portion of the fluid being circulated through said internal chamber to exit from said bit.

3. A rolling cutter rock bit for use with a drilling system that utilizes a gaseous flushing media for removing materials from the borehole, comprising:

a body;

a bearing shaft supported by said body;

a rolling cutter adapted to be rotatably mounted on said bearing shaft;

bearing means supporting said cutter on said bearing shaft;

a chamber within said body and adapted to be in communication with said gaseous flushing media;

a passage in said bearing shaft communicating between said chamber and said bearing means to divert said gaseous flushing media to said bearing means; and

screen means between said bearing shaft and said rolling cutter for preventing materials from the borehole from contacting said bearing means and allowing said gaseous flushing media to pass from said bearing means into the borehole.

4. A rotary rock bit suitable for use with a gaseous drilling fluid, comprising:

a head defining an internal chamber;

a bearing pin depending from said head;

a cone cutter adapted to be mounted on said bearing pin. said cone cutter having a concave cavity projecting from a cone mouth. said cavity and cone mouth positioned over said bearing pin;

bearing means located in said cavity supporting said cone cutter for rotation about said bearing pin;

a first passage through said head and said bearing pin communicating from said internal chamber to said cavity;

a second passage extending through said head communicating from said internal chamber to the exterior of said bit, whereby a first portion of the fluid being circulated through said internal chamber is circulated through said first passage to said cavity to cool said bearing means and a second portion of 7 the fluid being circulated through said internal chamber is circulated through said second passage proximate said cone cutter; and screen means positioned in said cone mouth between said cone cutter and said bearing pin for preventing entry of solids into said cavity and allowing said first portion of the fluid being circulated through said internal chamber to exit from said cavity.

5. A rolling cutter rock bit for use with a drilling system that utilizes a gaseous flushing media for removing materials from the borehole, comprising:

a body;

a bearing shaft supported by said body;

a rolling cutter adapted to be rotatably mounted on said bearing shaft;

borehole from contacting said bearing means and allowing said gaseous flushing media to pass from I said bearing means into said borehole; and an elastic means for positioning said screen means between said bearing shaft and said rolling cutter. 

1. A drill bit for connection with a drill string that includes a drilling fluid passage, comprising: a body; a bearing shaft supported from said body; a roller cutter adapted to be rotatably mounted on said bearing shaft; bearing means supporting said cutter on said bearing shaft; a passage within said body adapted to be in communication with the drilling fluid passage in said drill string when said drill bit is connected to the drill string; a passage in said bearing shaft communicating between said passage within said body and said bearing means; and screen means between said bearing shaft and said roller cutter.
 2. A drill bit for use with a circulating fluid, comprising: a head defining an internal chamber; a leg depending from said head; said leg terminating in a bearing shaft; a roller cutter adapted to be mounted on said bearing shaft; bearing means supporting said roller cutter for rotation about said bearing shaft; a first passage through said leg and said bearing shaft, communicating from said internal chamber to a position between said shaft and said cutter; a second passage extending through said bit communicating from said internal chamber to the exterior of said bit, whereby a first portion of the fluid being circulated through said internal chamber is circulated through said first passage, between said shaft and said cutter to cool said bearing means and a second portion of the fluid being circulated through said internal chamber is circulated through said second passage proximate said roller cutter; and screen means positioned between said cutter and said shaft for preventing entry of solids to said bearing means and allowing said first portion of the fluid being circulated through said internal chamber to exit from said bit.
 3. A rolling cutter rock bit for use with a drilling system that utilizes a gaseous flusHing media for removing materials from the borehole, comprising: a body; a bearing shaft supported by said body; a rolling cutter adapted to be rotatably mounted on said bearing shaft; bearing means supporting said cutter on said bearing shaft; a chamber within said body and adapted to be in communication with said gaseous flushing media; a passage in said bearing shaft communicating between said chamber and said bearing means to divert said gaseous flushing media to said bearing means; and screen means between said bearing shaft and said rolling cutter for preventing materials from the borehole from contacting said bearing means and allowing said gaseous flushing media to pass from said bearing means into the borehole.
 4. A rotary rock bit suitable for use with a gaseous drilling fluid, comprising: a head defining an internal chamber; a bearing pin depending from said head; a cone cutter adapted to be mounted on said bearing pin, said cone cutter having a concave cavity projecting from a cone mouth, said cavity and cone mouth positioned over said bearing pin; bearing means located in said cavity supporting said cone cutter for rotation about said bearing pin; a first passage through said head and said bearing pin communicating from said internal chamber to said cavity; a second passage extending through said head communicating from said internal chamber to the exterior of said bit, whereby a first portion of the fluid being circulated through said internal chamber is circulated through said first passage to said cavity to cool said bearing means and a second portion of the fluid being circulated through said internal chamber is circulated through said second passage proximate said cone cutter; and screen means positioned in said cone mouth between said cone cutter and said bearing pin for preventing entry of solids into said cavity and allowing said first portion of the fluid being circulated through said internal chamber to exit from said cavity.
 5. A rolling cutter rock bit for use with a drilling system that utilizes a gaseous flushing media for removing materials from the borehole, comprising: a body; a bearing shaft supported by said body; a rolling cutter adapted to be rotatably mounted on said bearing shaft; bearing means supporting said cutter on said bearing shaft; a chamber within said body and adapted to be in communication with said gaseous flushing media; a passage in said bearing shaft communicating between said chamber and said bearing means to divert said gaseous flushing media to said bearing means; screen means between said bearing shaft and said rolling cutter for preventing materials from the borehole from contacting said bearing means and allowing said gaseous flushing media to pass from said bearing means into said borehole; and an elastic means for positioning said screen means between said bearing shaft and said rolling cutter. 